The present disclosure relates to a self-actuated bleed valve for assisting start-up of a gas turbine engine.
Gas turbine engines are provided with a number of functional sections, including a fan section, a compressor section, a combustion section, and a turbine section. Air and fuel are combusted in the combustion section. The products of the combustion section move downstream, and pass over a series of turbine rotors in the turbine section, thereby driving the turbine rotors to provide power. The turbine rotors in the turbine section drive the compressor section and the fan section.
At start-up, the turbine section of the gas turbine engine takes time to fully provide power to the compressor section and fan section. Thus, driving the compressor section at start-up is more challenging for the turbine section than at steady state conditions. Prior art gas turbine engines generally include a bleed valve to bleed air away from the compressor section during start-up to reduce the load the turbine section experiences from the compressor section. The valve is open at start-up and moved to a closed position after start-up has been completed.
At least some prior art bleed valves include a poppet valve design that requires a large geometric area to meet a specified flow effective area. The large geometric area required by this poppet bleed valve can create a relatively tortuous flowpath for the air traveling through the poppet bleed valve, which leads to undesirable pressure losses. Furthermore, the poppet bleed valve is generally mounted to a bulkhead or duct in a cantilever fashion which can be prone to vibration issues. Additionally, this poppet bleed valve includes a fixed closing trigger pressure, which cannot be adjusted or recalibrated throughout the life of the valve.